Wafer processing apparatus and method, wafer convey robot, semiconductor substrate fabrication method, and semiconductor fabrication apparatus

ABSTRACT

A holder driving mechanism holds a wafer holder with gripping portions, and swings it within a wafer processing bath. When the peripheral portion of a wafer comes into contact with the distal end portion of a swing support member, the wafer rotates and vertically moves in the wafer holder. The wafer can be efficiently swung, and processing can be made uniform. By supplying ultrasonic waves from an ultrasonic bath, the processing rate can be increased.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a wafer processing apparatus andmethod, a wafer convey robot, a semiconductor substrate fabricationmethod, and a semiconductor fabrication apparatus and, moreparticularly, to a wafer processing apparatus and method which process awafer by dipping the wafer into a processing solution, a wafer conveyrobot suitable for this processing, and a semiconductor substratefabrication method and semiconductor fabrication apparatus to which theprocessing is applied.

[0003] 2. Description of the Related Art

[0004] Wet etching is a typical example of processing performed bydipping a wafer into a solution. One subject of wet etching is toimprove the in-plane uniformity. Conventionally, the in-plane uniformityis ensured by supplying fresh etching solution to the reaction surfaceby circulating the etching solution in a bath.

[0005] Another example of the processing performed by dipping a waferinto a solution is wafer cleaning processing. Japanese Patent Laid-OpenNo. 8-293478 has disclosed a wafer cleaning apparatus which increasesthe wafer cleaning efficiency by applying ultrasonic waves while dippingpart of a wafer into a solution and rotating the wafer.

[0006] The wafer cleaning apparatus disclosed in Japanese PatentLaid-Open No. 8-293478 rotates a wafer upon bringing the wafer intocontact with a rotating cam, which makes the cam and its accessoriesgenerate particles.

[0007] In this wafer cleaning apparatus, the strength of standing wavesof ultrasonic waves changes at the center and peripheral portion of thewafer. Since the cam obstructs the transmission of ultrasonic waves, theultrasonic waves cannot be uniformly supplied to the entire surface ofthe wafer. Accordingly, the wafer cannot be uniformly processed.

[0008] In the wafer cleaning apparatus, ultrasonic waves vibrate the camand the solution in the bath, and as a result, the wafer also vibrates.The wafer and the cam tend to slip with respect to each other, and thewafer cannot rotate uniformly.

[0009] In the wafer cleaning apparatus, when a wafer having anorientation flat is to be processed, the conditions for transmitting therotating force from the cam to the wafer change at the orientation flatand the remaining portion. For this reason, the wafer -cannot rotateuniformly.

SUMMARY OF THE INVENTION

[0010] The present invention has been made in consideration of the aboveproblems and has as its object to make wafer processing uniform.

[0011] It is another object of the present invention to preventcontamination of a wafer caused by particles.

[0012] A wafer processing apparatus according to the present inventionis a wafer processing apparatus for processing a wafer by dipping thewafer into a processing solution, characterized by comprising a waferprocessing bath, a holding portion for directly or indirectly holdingthe wafer, and a driving portion for supporting the holding portion fromabove the processing bath to swing the holding portion within theprocessing bath.

[0013] In the wafer processing apparatus, the driving portion preferablyalso serves as a convey mechanism for conveying the wafer between theapparatus and another apparatus.

[0014] The wafer processing apparatus preferably further comprisesultrasonic generating means for generating ultrasonic waves in theprocessing bath.

[0015] The wafer processing apparatus preferably further comprises aswing support member that comes into contact with a peripheral portionof the wafer in swinging the wafer by the driving portion, therebysupporting swinging by the driving portion.

[0016] In the wafer processing apparatus, a portion of the swing supportmember which may come into contact with the peripheral portion of thewafer is preferably rounded.

[0017] In the wafer processing apparatus, a portion of the swing supportmember which may come into contact with the peripheral portion of thewafer preferably has a groove in a direction substantially parallel to awafer surface.

[0018] In the wafer processing apparatus, the groove preferably has a Vshape.

[0019] In the wafer processing apparatus, the groove preferably has afull-wave rectifying shape.

[0020] In the wafer processing apparatus, the processing bath preferablycomprises a circulating mechanism including an overflow bath.

[0021] In the wafer processing apparatus, the driving portion preferablyswings the holding portion to rotate the wafer when the peripheralportion of the wafer comes into contact with the swing support member.

[0022] In the wafer processing apparatus, the ultrasonic generatingmeans preferably comprises an ultrasonic bath, an ultrasonic source, andan adjusting mechanism for adjusting a position of the ultrasonic sourcein the ultrasonic bath, and ultrasonic waves are preferably transmittedto the processing bath via an ultrasonic transmitting medium placed inthe ultrasonic bath.

[0023] In the wafer processing apparatus, the driving portion preferablycomprises a first driving portion for horizontally driving the holdingportion, and a second driving portion for vertically driving the holdingportion.

[0024] In the wafer processing apparatus, the holding portion preferablyholds the wafer substantially perpendicular to a bottom surface of theprocessing bath, and the driving portion preferably swings the waferwithin a plane substantially perpendicular to the bottom surface of theprocessing bath.

[0025] In the wafer processing apparatus, the driving portion preferablyswings the holding portion within the processing bath to substantiallyuniformly process the wafer with a processing solution.

[0026] In the wafer processing apparatus, the holding portion canpreferably hold a wafer holder capable of storing a plurality of wafers.

[0027] In the wafer processing apparatus, at least portions of theprocessing bath, the holding portion, and the driving portion, which maycome into contact with a processing solution, are preferably made of amaterial selected from the group consisting of quartz and plastic.

[0028] In the wafer processing apparatus, at least portions of theprocessing bath, the holding portion, and the driving portion, which maycome into contact with a processing solution, are preferably made of amaterial selected from the group consisting of a fluorine resin, vinylchloride, polyethylene, polypropylene, polybutyleneterephthalate (PBT),and polyetheretherketone (PEEK).

[0029] A wafer convey apparatus according to the present invention is awafer convey apparatus for conveying a wafer, characterized bycomprising a holding portion for directly or indirectly holding thewafer, and a driving portion for driving the holding portion along aconvey path, the driving portion dipping the wafer into a waferprocessing bath and swinging the wafer midway along the convey path.

[0030] In the wafer convey apparatus, the driving portion preferablycomprises a first driving portion for horizontally driving the holdingportion, and a second driving portion for vertically driving the holdingportion.

[0031] In the wafer convey apparatus, the holding portion preferablyholds the wafer substantially perpendicular to a bottom surface of theprocessing bath, and the driving portion preferably swings the waferwithin a plane substantially perpendicular to the bottom surface of theprocessing bath.

[0032] In the wafer convey apparatus, the driving portion preferablyswings the holding portion within the processing bath to substantiallyuniformly process the wafer with a processing solution in the processingbath.

[0033] In the wafer convey apparatus, the driving portion preferablyswings the holding portion within the processing bath to enhanceswinging of the wafer when a peripheral portion of the wafer comes intocontact with a projection formed in the processing bath.

[0034] In the wafer convey apparatus, the driving portion preferablyswings the holding portion within the processing bath to rotate thewafer when a peripheral portion of the wafer comes into contact with aprojection formed in the processing bath.

[0035] In the wafer convey apparatus, the holding portion can preferablyhold a wafer holder capable of storing a plurality of wafers.

[0036] A semiconductor fabrication apparatus according to the presentinvention is characterized by comprising the wafer convey apparatus, andone or a plurality of wafer processing apparatuses.

[0037] A wafer processing method according to the present invention is awafer processing method of processing a wafer by dipping the wafer intoa processing solution, characterized by comprising dipping a wafer intothe processing solution while supporting the wafer from above a waferprocessing bath, and swinging the wafer within the processing bath. Inthe wafer processing method, while the wafer is swung within theprocessing bath, ultrasonic waves are preferably generated in theprocessing solution.

[0038] In the wafer processing method, when the wafer is swung withinthe processing bath, a peripheral portion of the wafer is preferablybrought into contact with a projection formed in the processing bath toenhance swinging of the wafer.

[0039] In the wafer processing method, when the wafer is swung withinthe processing bath, a peripheral portion of the wafer is preferablybrought into contact with a projection formed in the processing bath torotate the wafer.

[0040] In the wafer processing method, the wafer is preferably swung tosubstantially uniformly process the wafer with the processing solution.

[0041] The wafer processing method is suitable for etching the wafer byusing an etching solution as the processing solution.

[0042] The wafer processing method is suitable for etching a waferhaving a porous silicon layer by using an etching solution as theprocessing solution.

[0043] An SOI wafer fabrication method according to the presentinvention is characterized by comprising fabricating an SOI wafer byusing the wafer processing method in a part of fabrication steps.

[0044] A wafer processing method according to the present invention ischaracterized by comprising processing a wafer by using the waferprocessing apparatus.

[0045] A wafer processing method according to the present invention ischaracterized by comprising etching a specific layer formed on a waferby using the wafer processing apparatus.

[0046] An SOI wafer fabrication method according to the presentinvention is characterized by comprising fabricating an SOI wafer byusing the wafer processing method in a part of fabrication steps.

[0047] A wafer processing method according to the present invention is awafer processing method of processing a wafer while supplying ultrasonicwaves, characterized by comprising completely dipping the wafer into aprocessing solution, and processing the wafer while changing a strengthof ultrasonic waves which act on the wafer.

[0048] A wafer processing method according to the present invention is awafer processing method of processing a wafer while supplying ultrasonicwaves, characterized by comprising completely dipping the wafer into aprocessing solution, and processing the wafer while moving the wafer.

[0049] A wafer processing method according to the present invention is awafer processing method of processing a wafer while supplying ultrasonicwaves, characterized by comprising completely dipping the wafer in aprocessing solution, and processing the wafer while swinging the wafer.

[0050] A wafer processing method according to the present invention is awafer processing method of processing a wafer while supplying ultrasonicwaves, characterized by comprising completely dipping the wafer in aprocessing solution, and processing the wafer while swinging the waferto cross a plane of vibration of ultrasonic waves.

[0051] A wafer processing method according to the present invention is awafer processing method of processing a wafer while supplying ultrasonicwaves, characterized by comprising completely dipping the wafer in aprocessing solution, supporting the wafer substantially perpendicular toa plane of vibration of ultrasonic waves, and processing the wafer whileswinging the wafer to cross the plane of vibration of ultrasonic waves.

[0052] A wafer processing method according to the present invention is awafer processing method of processing a wafer while supplying ultrasonicwaves, characterized by comprising completely dipping the wafer in aprocessing solution, supporting the wafer substantially parallel to aplane of vibration of ultrasonic waves, and processing the wafer whileswinging the wafer to cross the plane of vibration of ultrasonic waves.

[0053] A semiconductor substrate fabrication method according to thepresent invention is characterized by comprising the step of forming anunporous layer on a porous layer formed on a surface of a firstsubstrate, the step of adhering a first substrate side of a prospectivestructure and a second substrate prepared separately to sandwich theunporous layer between the first substrate side and the secondsubstrate, the removal step of removing the first substrate from theadhered structure to expose the porous layer on a second substrate sidethereof, and the etching step of etching the porous layer while thesecond substrate side on which the porous layer is exposed is completelydipped into an etching solution, and ultrasonic waves are supplied,thereby exposing a surface of the second substrate side, the etchingstep changing a strength of ultrasonic waves which act on the secondsubstrate side.

[0054] A semiconductor substrate fabrication method according to thepresent invention is characterized by comprising the step of forming anunporous layer on a porous layer formed on a surface of a firstsubstrate, the step of adhering a first substrate side of a prospectivestructure and a second substrate prepared separately to sandwich theunporous layer between the first substrate side of a prospectivestructure and the second substrate, the removal step of removing thefirst substrate from the adhered structure to expose the porous layer ona second substrate side thereof, and the etching step of etching theporous layer while the second substrate side on which the porous layeris exposed is completely dipped into an etching solution, and ultrasonicwaves are supplied, thereby exposing a surface of the second substrateside, the etching step moving the second substrate side.

[0055] A semiconductor substrate fabrication method according to thepresent invention is characterized by comprising the step of forming anunporous layer on a porous layer formed on a surface of a firstsubstrate, the step of adhering a first substrate side of a prospectivestructure and a second substrate prepared separately to sandwich theunporous layer between the first substrate side and the secondsubstrate, the removal step of removing the first substrate from theadhered structure to expose the porous layer on a second substrate sidethereof, and the etching step of etching the porous layer while thesecond substrate side on which the porous layer is exposed is completelydipped into an etching solution, and ultrasonic waves are supplied,thereby exposing a surface of the second substrate side, the etchingstep swinging the second substrate side.

[0056] A semiconductor substrate fabrication method according to thepresent invention is characterized by comprising the step of forming anunporous layer on a porous layer formed on a surface of a firstsubstrate, the step of adhering a first substrate side of a prospectivestructure and a second substrate prepared separately to sandwich theunporous layer between the first substrate side and the secondsubstrate, the removal step of removing the first substrate from theadhered structure to expose the porous layer on a second substrate sidethereof, and the etching step of etching the porous layer while thesecond substrate side on which the porous layer is exposed is completelydipped into an etching solution, and ultrasonic waves are supplied,thereby exposing a surface of the second substrate side, the etchingstep swinging the second substrate side to cross a plane of vibration ofultrasonic waves.

[0057] A semiconductor substrate fabrication method according to thepresent invention is characterized by comprising the step of forming anunporous layer on a porous layer formed on a surface of a firstsubstrate, the step of adhering a first substrate side of a prospectivestructure and a second substrate prepared separately to sandwich theunporous layer between the first substrate side and the secondsubstrate, the removal step of removing the first substrate from theadhered structure to expose the porous layer on a second substrate sidethereof, and the etching step of etching the porous layer while thesecond substrate side on which the porous layer is exposed is completelydipped into an etching solution and supported substantiallyperpendicular to a plane of vibration of ultrasonic waves, andultrasonic waves are supplied, thereby exposing a surface of the secondsubstrate side, the etching step swinging the second substrate side tocross the plane of vibration of ultrasonic waves.

[0058] A semiconductor substrate fabrication method according to-thepresent invention is characterized by comprising the step of forming anunporous layer on a porous layer formed on a surface of a firstsubstrate, the step of adhering a first substrate side of a prospectivestructure and a second substrate prepared separately to sandwich theunporous layer between the first substrate side and the secondsubstrate, the removal step of removing the first substrate from theadhered structure to expose the porous layer on a second substrate sidethereof, and the etching step of etching the porous layer while thesecond substrate side on which the porous layer is exposed is completelydipped into an etching solution and supported substantially parallel toa plane of vibration of ultrasonic waves, and ultrasonic waves aresupplied, thereby exposing a surface of the second substrate side, theetching step swinging the second substrate side to cross the plane ofvibration of ultrasonic waves.

[0059] Further objects, features and advantages of the present inventionwill become apparent from the following detailed description ofembodiments of the present invention with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0060]FIG. 1A is a view showing an outline of the construction of awafer processing apparatus according to a preferred embodiment of thepresent invention;

[0061]FIG. 1B is a view showing an outline of the construction of aholder driving mechanism;

[0062]FIGS. 2A to 2E are views for explaining a wafer swinging method;

[0063]FIG. 3 is a view showing an example of the construction of a swingsupport member;

[0064]FIGS. 4A and 4B are views each showing another example of theconstruction of the swing support member;

[0065]FIG. 5A is a perspective view showing an outline of theconstruction of a wafer processing system incorporating the waferprocessing apparatus;

[0066]FIG. 5B is a front view showing an outline of the construction ofthe wafer processing system incorporating the wafer processingapparatus;

[0067]FIGS. 6A to 6D are views for explaining another example of thewafer swinging method;

[0068]FIG. 7 is a view showing an outline of the construction of a waferprocessing apparatus according to another embodiment of the presentinvention; and

[0069]FIGS. 8A to 8F are views, respectively, showing a method offabricating a semiconductor substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0070] A preferred embodiment of the present invention will be describedbelow with reference to the accompanying drawings.

[0071] [First Embodiment]

[0072]FIG. 1A is a view showing an outline of the construction of awafer processing apparatus according to the preferred embodiment of thepresent invention. The wafer processing apparatus according to thisembodiment can be widely applied to etching, cleaning, and anotherprocessing which supplies a processing solution to a wafer.

[0073] In a wafer processing apparatus 100 according to this embodiment,portions which may come into contact with a processing solution arepreferably made from quartz or plastic in accordance with the intendeduse. Preferable examples of the plastic are a fluorine resin, vinylchloride, polyethylene, polypropylene, polybutyleneterephthalate (PBT),and polyetheretherketone (PEEK). Preferable examples of the fluorineresin are PVDF, PFA, and PTFE.

[0074] This wafer processing apparatus 100 has a wafer processing bath11, and a holder driving mechanism 31 for swinging a wafer holder 21 inthe wafer processing bath 11. The wafer processing apparatus 100preferably comprises an ultrasonic bath 61.

[0075] To process wafers, the wafer processing bath 11 is filled with aprocessing solution. A 4-plane overflow bath 12 is mounted on the waferprocessing bath 11, and supplies a processing solution from the bottomportion of the wafer processing bath 11 into the wafer processing bath11 by a circulator 71 incorporating a filter. The processing solutionoverflowing from the wafer processing bath 11 is stored in the 4-planeoverflow bath 12, and discharged from the bottom portion of the 4-planeoverflow bath 12 toward the circulator 71. Since the wafer processingapparatus 100 agitates the processing solution while swinging the waferholder 21 by the holder driving mechanism 31, the liquid level of theprocessing solution can be kept constant. Therefore, the circulatingsystem including the 4-plane overflow bath 12 is very useful.

[0076] The wafer holder 21 may be a commercially available product, andis preferably made from quartz or plastic. Preferable examples of theplastic are a fluorine resin, vinyl chloride, polyethylene,polypropylene, polybutyleneterephthalate (PBT), and polyetheretherketone(PEEK). Preferable examples of the fluorine resin are PVDF, PFA, andPTFE.

[0077] The holder driving mechanism 31 has a pair of gripping portions31 a for gripping the wafer holder 21. The wafer holder 21 is gripped bythe pair of gripping portions 31 a and dipped in the wafer processingbath 11. While the wafer holder 21 is swung within the wafer processingbath 11, desired processing can be performed for a wafer 41. The holderdriving mechanism 31 functions to convey the wafer holder 21 holding thewafer 41 having undergone previous processing to the wafer processingbath 11 or the next processing, whereas it functions as part of thewafer processing apparatus 100.

[0078] In this embodiment, the wafer 41 is indirectly held by holdingthe wafer holder 21 with the gripping portions 31 a. Alternatively, thewafer 41 can be directly held by, e.g., a chucking pad in place of thegripping portions 31 a. The direction to hold the wafer 41 is notlimited to a direction perpendicular to the bottom surface of the waferprocessing bath 11, and may be a direction parallel to the bottomsurface.

[0079] A swing support member 13 for increasing the swing efficiency ofthe wafer 41 in swinging the wafer 41 by the holder driving mechanism 31is preferably arranged at the bottom portion of the wafer processingbath 11. When the wafer holder 21 moves, the swing support member 13contacts the peripheral portion of the wafer 41 held by the wafer holder21 to rotate the wafer 41 by the frictional force and vertically move itwithin the wafer holder 21. The swing support member 13 is useful forimproving the in-plane uniformity of the processed wafer.

[0080] It is also effective to arrange a driving mechanism for movingthe swing support member 13 vertically (y-axis direction) and/orhorizontally (x-axis direction). In this case, the swing support member13 itself can move to rotate the wafer 41 and vertically move it withinthe wafer holder 21. Accordingly, the moving range of the wafer holder21 by the holder driving mechanism 31 can be reduced, and in otherwords, the wafer processing bath 11 can be downsized.

[0081] An ultrasonic source 51 is arranged in the ultrasonic bath 61,and filled with an ultrasonic transmitting medium (e.g., water). Theultrasonic source 51 is fixed to an adjusting mechanism 62 forvertically and/or horizontally adjusting the position of the ultrasonicsource 51. Ultrasonic waves to be supplied to the wafer processing bath11, more specifically, to the wafer 41 can be optimized by adjusting thepositional relationship between the ultrasonic source 51 and the waferprocessing bath 11 by the adjusting mechanism 62. The ultrasonic source51 preferably has a function of adjusting the frequency or strength ofultrasonic waves to be generated. This can further optimize the supplyof ultrasonic waves. Since the ultrasonic source 51 has the function foroptimizing the supply of ultrasonic waves to the wafer 41, various typesof wafers can be processed.

[0082]FIG. 1B is a view showing an outline of the construction of theholder driving mechanism 31. The gripping portions 31 a are opened byextending opening/closing rods 31 b, and closed by contracting theserods 31 b. The holder driving mechanism 31 moves in the x-axis directionalong a horizontal driving shaft 31 c and in the y-axis direction alonga vertical driving shaft 31 d.

[0083]FIGS. 2A to 2E are views for explaining a wafer swinging method.In FIGS. 2A to 2E, the arrows indicate the moving direction of the waferholder 21. FIG. 2A shows a state immediately before starting swinging awafer. When the start of wafer swinging is instructed, the holderdriving mechanism 31 depresses the gripping portions 31 a downward undercomputer control, as shown in FIG. 2B. During this depression, theperipheral portion of the wafer 41 comes into contact with the swingsupport member 13. As a result, the lower portion of the wafer 41 issupported by the swing support member 13.

[0084] The swing support member 13 may generate a few particles uponcontact with the wafer 41. The swing support member 13 preferablysmoothly contacts the wafer 41 by rounding the distal end portion of theswing support member 13, as shown in FIG. 3.

[0085] Since the swing support member 13 suffices to support the swingof the wafer 41, it can be formed into a shape, e.g., a thin plate notto obstruct the transmission of ultrasonic waves. With this shape, theultrasonic waves to be supplied to the wafer 41 can be uniformed touniformly process the wafer 41.

[0086] Slight ultrasonic nonuniformity caused by the swing supportmember 13 does not pose any problem because the wafer processingapparatus 100 processes the wafer 41 while changing the relativepositional relationship between the wafer 41 and the swing supportmember 13, in other words, the relative positional relationship betweenthe wafer 41 and the wafer processing bath 11.

[0087] Since a slightly larger depression amount of the wafer holder 21can increase the contact pressure between the wafer 41 and the swingsupport member 13, a slip between the swing support member 13 and thewafer 41 can be prevented to prevent operation failure. This is because,if the depression amount is too small, the gravity for the wafer 41 actson the wafer holder 21 more greatly than on the distal end portion ofthe swing support member 13. When the swing support member 13 having theshape according to this embodiment is used, the depression amount ispreferably about 30 mm after the wafer 41 comes into contact with theswing support member 13.

[0088] Upon depressing the wafer holder 21, the holder driving mechanism31 moves the gripping portions 31 a rightward (positive direction of theX axis) under computer control, as shown in FIG. 2C. As a result, thewafer 41 substantially horizontally moves rightward (positive directionof the X axis) in the wafer processing bath 11 while rotating clockwise.The moving amount of the gripping portions 31 a must be set to fallwithin the range in which these gripping portions 31 a do not collideagainst an opening portion at the lower portion of the wafer holder 21.

[0089] After the wafer holder 21 has moved rightward (positive directionof the X axis), the holder driving mechanism 31 vertically moves thegripping portions 31 a under computer control, as shown in FIG. 2D. Themoving amount of the gripping portions 31 a preferably falls within therange in which the wafer 41 does not come close to a liquid surface 14of the processing solution. This is because particles may attach to thesurface of the wafer 41 if the wafer 41 comes close to the liquidsurface 14.

[0090] Upon completion of the upward movement of the wafer holder 21,the holder driving mechanism 31 moves the gripping portions 31 aleftward (negative direction of the X axis) under computer control toreturn them in the initial state (FIG. 2A), as shown in FIG. 2E.

[0091] By repeatedly performing the above operation (FIG. 2A→FIG.2B→FIG. 2C→FIG. 2D→FIG. 2E), the wafer 41 can be properly swung anduniformly processed.

[0092] According to the wafer processing apparatus 100, since the wafer41 is swung in the region where the supply of ultrasonic waves isoptimized by adjusting the ultrasonic bath 61, ultrasonic waves whichact on the wafer 41 can be optimized.

[0093] The standing waves of ultrasonic waves have loops (high-strengthportions) and nodes (low-strength portions) at constant separation.Therefore, ultrasonic waves are difficult to uniform in the waferprocessing bath 11.

[0094] However, since the wafer processing apparatus 100 swings thewafer 41 with the holder driving mechanism 31, it can uniformly processthe wafer 41 regardless of a somewhat nonuniform distribution of theultrasonic wave strength. Even if the direction to move the wafer 41 isa simple direction such as only the horizontal, vertical, or obliquedirection, it can contribute to the processing uniformity of the wafer41. By swinging the wafer 41 in its axial direction (z-axis direction),the processing nonuniformity between wafers attributed to high-strengthportions of ultrasonic waves in the horizontal plane can be corrected.

[0095] Since the wafer processing apparatus 100 further comprises theswing support member 13, the swinging amount of the wafer 41 can beefficiently increased. The fixed position of the swing support member 13is not limited to the bottom portion of the wafer processing bath 11. Asfar as the swing support member 13 can contact with all wafers 41 of thewafer holder 21, it can be fixed to, e.g., the side wall of the waferprocessing bath 11 or the holder driving mechanism 31 (in this case, amechanism of changing the relative positional relationship between theswing support member 13 and the gripping portions 31 a is arranged).

[0096] According to the wafer processing apparatus 100, since no drivingmechanism exists in the wafer processing bath 11, no particle isproduced by the driving mechanism.

[0097] Even if the wafer processing apparatus 100 does not comprise anyultrasonic bath 61, it can function as an apparatus suitable for waferprocessing. More specifically, if the wafer processing apparatus 100 hasa function of swinging the wafer holder 21 within the wafer processingbath 11 by the holder driving mechanism 31, it can uniformly process thewafer 41 with only this function, and effectively agitate the processingsolution. A gas or the like produced upon processing the wafer 41 can beefficiently removed from the surface of the wafer 41. Since the holderdriving mechanism 31 can serve as both convey and swinging mechanismsfor the wafer 41, wafers can be efficiently processed.

[0098]FIG. 4A is an overall view of another example of the constructionof the swing support member 13. FIG. 4B is an enlarged view of part ofthe swing support member 13. If the strength of ultrasonic waves ishigh, the distal end portion of the swing support member 13 and thewafer 41 may slip and fail to efficiently swing the wafer 41.

[0099] A swing support member 13′ shown in FIGS. 4A and 4B has V-shapedgrooves 13 a at constant intervals. By forming these V-shaped grooves 13a, the contact area with the wafers 41 can be increased. Since the swingsupport member 13′ engages with the wafer 41 so as to pinch it, theswing efficiency of the wafer 41 increases. Even if the wafer 41vibrates to be temporarily spaced apart from the swing support member13′, the frictional force with the wafer 41 does not decrease unless thewafer 41 accurately vertically moves.

[0100] The groove at the distal end portion of the swing support member13′ may have a shape 13 b, i.e., a full-wave rectifying shape. In thiscase, since the groove does not have any top, unlike the V-shaped groove13 a, generation of particles upon contact with the wafer 41 can besuppressed.

[0101] [Second Embodiment]

[0102]FIG. 5A is a perspective view showing an outline of theconstruction of a wafer processing system incorporating a waferprocessing apparatus 100. FIG. 5B is a front view showing part of thewafer processing system shown in FIG. 5A.

[0103] This wafer processing system is preferably a combination of aloader, a wafer processing apparatus (e.g., an etching or cleaningapparatus), a spin dryer, an unloader, and the like.

[0104] Reference numeral 31′ denotes a holder driving mechanism havingsubstantially the same function as that of the holder driving mechanism31, which has gripping portions 31 a″ for gripping a wafer holder 21, ameans for driving the wafer holder 21 horizontally (alignment directionof the respective apparatuses), and a means for vertically driving thewafer holder 21.

[0105] This wafer processing system can automatically process a waferunder computer control. Particles produced by the intervention of theoperator can be prevented from attaching to wafers, and the processingefficiency can be increased.

[0106] [Third Embodiment]

[0107] The third embodiment will exemplify another wafer swingingmethod. FIGS. 6A to 6D are views for explaining a wafer swinging methodin this embodiment. In FIGS. 6A to 6D, the arrows indicate the movingdirection of a wafer holder 21. FIG. 6A shows a state immediately beforestarting swinging a wafer. When the start of wafer swinging isinstructed, a holder driving mechanism 31 moves gripping portions 31 adownwardly to the right under computer control, as shown in FIG. 6B. Themoving direction is suitably at an angle of about 45° with respect tothe horizontal plane. When the wafer holder 21 has moved downwardly tothe right, a wafer 41 rotates clockwise about the distal end portion ofa swing support member 13 while its peripheral portion is pressed by theleft side wall of the wafer holder 21.

[0108] After the wafer holder 21 has moved downwardly to the right, thecenter of gravity of the wafer 41 moves to the right with respect to thedistal end portion of the swing support member 13, and the wafer 41rotates toward the right side wall of the wafer holder 21 to settle to astate shown in FIG. 6C.

[0109] Upon moving the wafer holder 21 downwardly to the right, theholder driving mechanism 31 moves the gripping portions 31 a upwardly tothe left, as shown in FIG. 6D. The moving direction is preferablyopposite to the moving direction shown in FIG. 6B.

[0110] When the wafer holder 21 has moved upwardly to the left, thewafer 41 rotates counterclockwise about the swing support member 13while its peripheral portion is pressed by the right side wall of thewafer holder 21. By moving the wafer holder 21 to a state shown in FIG.6A, one operation is completed.

[0111] By repeatedly performing the above operation (FIG. 6A→FIG.6B→FIG. 6C→FIG. 6D), the wafer 41 can be properly swung and uniformlyprocessed.

[0112] [Fourth Embodiment]

[0113] The fourth embodiment is directed to a wafer processing apparatushaving another construction. FIG. 7 is a view showing an outline of theconstruction of the wafer processing apparatus according to thisembodiment. The same reference numerals as in the construction of thewafer processing apparatus 100 according to the first embodiment denotesubstantially the same constituent elements, and a description thereofwill be omitted.

[0114] A wafer processing apparatus 101 according to the fourthembodiment holds a wafer 41 with a wafer moving mechanism 80 almostparallel to the bottom surface of a wafer processing bath 11 (i.e.,almost parallel to the plane of vibration of ultrasonic waves), andswings the wafer 41 while completely dipping it into a processingsolution (e.g., cleaning or etching solution) within the waferprocessing bath 11. In this manner, the wafer 41 is uniformly processed,and contamination of the wafer 41 by particles is prevented.

[0115] The wafer moving mechanism 80 grips the wafer 41 with arms 81,and swings the wafer 41 in the wafer processing bath 11. The wafer 41 ispreferably swung in a direction perpendicular to the plane of vibrationof ultrasonic waves (i.e., vertical direction), or in a directionparallel to the plane of vibration (i.e., horizontal direction).

[0116] Also in the wafer processing apparatus 101, the wafer 41 ispreferably processed while being completely dipped into the processingsolution. In this case, particles can be prevented from attaching to thewafer 41 near the interface between the processing solution and ambientatmosphere.

[0117] According to the wafer processing apparatus 101, the wafer 41 canbe uniformly processed by swinging it in the wafer processing bath 11.

[0118] [Application of Wafer Processing Apparatus]

[0119] The wafer processing apparatus 100 according to the aboveembodiments is suitable as, e.g., an etching apparatus. According tothis etching apparatus, 1) a wafer can be uniformly etched, 2)contamination by particles can be reduced, and 3) the etching rate canbe increased.

[0120] The wafer processing apparatus 100 is suited as an etchingapparatus for etching a wafer having a porous silicon layer. Themechanism of etching of porous silicon is disclosed in K. Sakaguchi etal., Jpn. Appl. Phys. Vol. 34, part 1, No. 2B, 842-847 (1995). Poroussilicon is etched when an etching solution penetrates into the pores ofporous silicon by a capillary action and etches the walls of the pores.As the walls of the pores become thinner, these walls cannot supportthemselves beyond some point. Finally, the porous layer entirelycollapses to complete the etching. When the pore walls are left tocollapse by the action of only the etching solution without any etchingassistance, the etching rate of the hole wall is low, and the etchingtime is long. In a region where the porous layer collapses, theunderlayer is etched. For this reason, variations in in-plane etchingrate of a porous silicon wafer and etching rate between wafers arepreferably suppressed as much as possible.

[0121] For example, a first substrate is prepared by forming a poroussilicon layer on a single-crystal silicon substrate, growing anepitaxial layer on the porous silicon layer, and forming an insulatingfilm on the epitaxial layer. The first substrate and a second substrateare so adhered as to sandwich the insulating film between them. Then,the single-crystal silicon substrate is removed from the lower surfaceof the first substrate, and the porous silicon layer is etched tofabricate an SOI wafer. This method requires an etching selectivity(porous silicon/epitaxial layer) of only about 10⁵.

[0122] Even if an etching method having high selectivity is employed,however, the surface of the SOI layer exposed upon removing the poroussilicon layer by etching is slightly etched. Such slight unwantedetching does not seriously degrade the thickness uniformity of the SOIlayer, but higher selectivity and higher thickness uniformity aredemanded. In the future, as the wafer size increases, higher thicknessuniformity of the SOI layer will be demanded.

[0123] When the wafer processing apparatus 100 is applied to a poroussilicon etching apparatus, in-plane variations of the SOI layer andvariations between wafers can be suppressed by swinging wafers withinthe wafer processing bath, and higher-quality SOI substrates can befabricated.

[0124] By swinging wafers, and in addition, performing etching whilesupplying ultrasonic waves, the collapse of the porous silicon layer canbe promoted, the etching time can be shortened, and the etchingselectivity can be increased.

[0125] An example of a method of fabricating a semiconductor substrateusing the wafer processing apparatus according to the above embodimentswill be described below.

[0126]FIGS. 8A to 8F are views, respectively, showing the method offabricating a semiconductor substrate. Roughly speaking, in thisfabrication method, the first substrate is prepared by forming a poroussilicon layer on a single-crystal silicon substrate, forming an unporouslayer on the porous silicon layer, and preferably forming an insulatingfilm on the unporous layer. The first structure and a second substrateprepared separately are so adhered as to sandwich the insulating filmbetween them. After that, the single-crystal silicon substrate isremoved from the lower surface of the first substrate, and the poroussilicon layer is etched to fabricate a semiconductor substrate.

[0127] The method of fabricating a semiconductor substrate will bedescribed in detail below with reference to FIGS. 8A to 8F.

[0128] A single-crystal Si substrate 501 for forming the first substrateis prepared, and a porous Si layer 502 is formed on the major surface ofthe single-crystal Si substrate 501 (see FIG. 8A). At least one unporouslayer 503 is formed on the porous Si layer 502 (see FIG. 8B). Preferableexamples of the unporous layer 503 are a single-crystal Si layer, apoly-Si layer, an amorphous Si layer, a metal film layer, a compoundsemiconductor layer, and a superconductor layer. An element such asMOSFET may be formed on the unporous layer 503.

[0129] An SiO₂ layer 504 is preferably formed as another unporous layeron the unporous layer 503, and used as the first substrate (see FIG.8C). The SiO₂ layer 504 is useful because, when the first substrate anda second substrate 505 are adhered in the subsequent step, the interfaceenergy at the adhered interface can be removed from an active layer.

[0130] The first substrate and the second substrate 505 are tightlyadhered at room temperature so as to sandwich the SiO₂ layer 504 betweenthem (see FIG. 8D). This adhesion may be strengthened by performinganode coupling, pressurization, or heat treatment, as needed, or acombination of them.

[0131] When a single-crystal Si layer is formed as the unporous layer503, the first substrate is preferably adhered to the second substrate505 after the SiO₂ layer 504 is formed on the surface of thesingle-crystal Si layer by thermal oxidization or the like.

[0132] Preferable examples of the second substrate 505 are an Sisubstrate, a substrate having an SiO₂ layer formed on an Si substrate, alight-transmitting substrate such as a quartz substrate or the like, anda sapphire substrate. The second substrate 505 suffices to have a flatsurface to be adhered, and may be another type of substrate.

[0133]FIG. 8D shows the adhered state of the first and second substratesvia the SiO₂ layer 504. The SiO₂ layer 504 need not be formed when theunporous layer 503 or the second substrate is not Si.

[0134] In adhesion, a thin insulating plate may be inserted between thefirst and second substrates.

[0135] The first substrate is removed from the second substrate at theboundary of the porous Si layer 502 (see FIG. 8E). The removal methodincludes the first method (of discarding the first substrate) usinggrinding, polishing, etching, or the like, and the second method ofseparating the first and second substrates at the boundary of the porouslayer 502. In the second method, the first substrate can be recycled byremoving porous Si left on the separated first substrate, andplanarizing the surface of the first substrate, as needed.

[0136] The porous Si layer 502 is selectively etched and removed (seeFIG. 8F). The wafer processing apparatus 100 or 101 is suitable for thisetching. Since this wafer processing apparatus supplies ultrasonic waveswhile completely dipping a wafer (in this case, the wafer shown in FIG.8E) into an etching solution and swinging it, the wafer is hardlycontaminated by particles, and the etching is made uniform. According tothis wafer processing apparatus, the etching time is shortened, and theetching selectivity between the unporous layer 503 and the porous layer504 increases. The etching time is shortened because etching is promotedby ultrasonic waves, and the etching selectivity increases because thepromotion of etching by ultrasonic waves is more remarkable on theporous layer 504 than on the unporous layer 503.

[0137] When the unporous layer 503 is single-crystal Si, the followingetching solutions are suited in addition to a general etching solutionfor Si.

[0138] (a) hydrofluoric acid

[0139] (b) solution mixture prepared by adding at least one of alcoholand hydrogen peroxide to hydrofluoric acid

[0140] (c) buffered hydrofluoric acid

[0141] (d) solution mixture prepared by adding at least one of alcoholand hydrogen peroxide to buffered hydrofluoric acid

[0142] (e) solution mixture of hydrofluoric acid, nitric acid, andacetic acid

[0143] Using these etching solutions, the porous layer 502 can beselectively etched to leave the underlying unporous layer 503(single-crystal Si). The porous layer 502 is readily selectively etchedby these etching solutions because porous Si has an enormous surfacearea and hence etching progresses at a very high speed for the unporousSi layer.

[0144]FIG. 8E schematically shows a semiconductor substrate obtained bythe above fabrication method. According to this fabrication method, theflat unporous layer 503 (e.g., single-crystal Si layer) is uniformlyformed on the entire surface of the second substrate 505.

[0145] For example, if an insulating substrate is employed as the secondsubstrate 505, the semiconductor substrate obtained by the abovefabrication method is effectively used to form insulated electronicelements.

[0146] The present invention can make wafer processing uniform, and canprevent contamination of a wafer caused by particles.

[0147] The present invention is not limited to the above embodiments andvarious changes and modifications can be made within the spirit andscope of the present invention. Therefore, to apprise the public of thescope of the present invention the following claims are made.

What is claimed is:
 1. A wafer processing apparatus for processing awafer by dipping the wafer into a processing solution, comprising: awafer processing bath; a holding portion for directly or indirectlyholding the wafer; and a driving portion for supporting said holdingportion from above said processing bath to swing said holding portionwithin said processing bath.
 2. The apparatus according to claim 1,wherein said driving portion also serves as a convey mechanism forconveying the wafer between the apparatus and another apparatus.
 3. Theapparatus according to claim 1, further comprising ultrasonic generatingmeans for generating ultrasonic waves in said processing bath.
 4. Theapparatus according to claim 1, further comprising a swing supportmember that comes into contact with a peripheral portion of the wafer inswinging the wafer by said driving portion, thereby supporting swingingby said driving portion.
 5. The apparatus according to claim 4, whereina portion of said swing support member which may come into contact withthe peripheral portion of the wafer is rounded.
 6. The apparatusaccording to claim 4, wherein a portion of said swing support memberwhich may come into contact with the peripheral portion of the wafer hasa groove in a direction substantially parallel to a wafer surface. 7.The apparatus according to claim 6, wherein the groove has a V shape. 8.The apparatus according to claim 6, wherein the groove has a rectifiedfull-wave shape.
 9. The apparatus according to claim 1, wherein saidprocessing bath comprises a circulating mechanism including an overflowbath.
 10. The apparatus according to claim 4, wherein said drivingportion swings said holding portion to rotate the wafer when theperipheral portion of the wafer comes into contact with said swingsupport member.
 11. The apparatus according to claim 3, wherein saidultrasonic generating means comprises an ultrasonic bath, an ultrasonicsource, and an adjusting mechanism for adjusting a position of saidultrasonic source in said ultrasonic bath, and ultrasonic waves aretransmitted to said processing bath via an ultrasonic transmittingmedium placed in said ultrasonic bath.
 12. The apparatus according toclaim 1, wherein said driving portion comprises a first driving portionfor horizontally driving said holding portion, and a second drivingportion for vertically driving said holding portion.
 13. The apparatusaccording to claim 1, wherein said holding portion holds the wafersubstantially perpendicular to a bottom surface of said processing bath,and said driving portion swings the wafer within a plane substantiallyperpendicular to the bottom surface of said processing bath.
 14. Theapparatus according to claim 1, wherein said driving portion swings saidholding portion within said processing bath to substantially uniformlyprocess the wafer with a processing solution.
 15. The apparatusaccording to claim 1, wherein said holding portion can hold a waferholder capable of storing a plurality of wafers.
 16. The apparatusaccording to claim 1, wherein at least portions of said processing bath,said holding portion, and said driving portion, which may come intocontact with a processing solution, are made of a material selected fromthe group consisting of quartz and plastic.
 17. The apparatus accordingto claim 1, characterized in that at least portions of said processingbath, said holding portion, and said driving portion, which may comeinto contact with a processing solution, are made of a material selectedfrom the group consisting of a fluorine resin, vinyl chloride,polyethylene, polypropylene, polybutyleneterephthalate (PBT), andpolyetheretherketone (PEEK).
 18. A wafer convey apparatus for conveyinga wafer, comprising: a holding portion for directly or indirectlyholding the wafer; and a driving portion for driving said holdingportion along a convey path, said driving portion dipping the wafer intoa wafer processing bath and swinging the wafer midway along the conveypath.
 19. The apparatus according to claim 18, wherein said drivingportion comprises a first driving portion for horizontally driving saidholding portion, and a second driving portion for vertically drivingsaid holding portion.
 20. The apparatus according to claim 18, whereinsaid holding portion holds the wafer substantially perpendicular to abottom surface of said processing bath, and said driving portion swingsthe wafer within a plane substantially perpendicular to the bottomsurface of said processing bath.
 21. The apparatus according to claim18, wherein said driving portion swings said holding portion within saidprocessing bath to substantially uniformly process the wafer with aprocessing solution in said processing bath.
 22. The apparatus accordingto claim 18, wherein said driving portion swings said holding portionwithin said processing bath to enhance swinging of the wafer when aperipheral portion of the wafer comes into contact with a projectionformed in said processing bath.
 23. The apparatus according to claim 18,wherein said driving portion swings said holding portion within saidprocessing bath to rotate the wafer when a peripheral portion of thewafer comes into contact with a projection formed in said processingbath.
 24. The apparatus according to claim 18, wherein said holdingportion can hold a wafer holder capable of storing a plurality ofwafers.
 25. A semiconductor fabrication apparatus comprising theapparatus according to claim 18, and one or a plurality of waferprocessing apparatuses.
 26. A wafer processing method of processing awafer by dipping the wafer into a processing solution, comprisingdipping a wafer into the processing solution while supporting the waferfrom above a wafer processing bath, and swinging the wafer within saidprocessing bath.
 27. The method according to claim 26, wherein, whilethe wafer is swung within said processing bath, ultrasonic waves aregenerated in the processing solution.
 28. The method according to claim26, wherein, when the wafer is swung within said processing bath, aperipheral portion of the wafer is brought into contact with aprojection formed in said processing bath to enhance swinging of thewafer.
 29. The method according to claim 26, wherein, when the wafer isswung within said processing bath, a peripheral portion of the wafer isbrought into contact with a projection formed in said processing bath torotate the wafer.
 30. The method according to claim 26, wherein thewafer is swung to substantially uniformly process the wafer with theprocessing solution.
 31. The method according to claim 26, wherein thewafer is etched by using an etching solution as the processing solution.32. The method according to claim 26, wherein a wafer having a poroussilicon layer is etched by using an etching solution as the processingsolution.
 33. A semiconductor substrate fabrication method comprisingfabricating a semiconductor substrate by using the method according toclaim 32 in a part of fabrication steps.
 34. A wafer processing methodcomprising processing a wafer by using the apparatus according toclaim
 1. 35. A wafer processing method comprising etching a specificlayer formed on a wafer by using the apparatus according to claim
 1. 36.A semiconductor substrate fabrication method comprising fabricating asemiconductor substrate by using the method according to claim 35 in apart of fabrication steps.
 37. A wafer processing method of processing awafer while supplying ultrasonic waves, comprising: completely dippingthe wafer into a processing solution, and processing the wafer whilechanging a strength of ultrasonic waves which act on the wafer.
 38. Awafer processing method of processing a wafer while supplying ultrasonicwaves, comprising: completely dipping the wafer into a processingsolution, and processing the wafer while moving the wafer.
 39. A waferprocessing method of processing a wafer while supplying ultrasonicwaves, comprising: completely dipping the wafer in a processingsolution, and processing the wafer while swinging the wafer.
 40. A waferprocessing method of processing a wafer while supplying ultrasonicwaves, comprising: completely dipping the wafer in a processingsolution, and processing the wafer while swinging the wafer to cross aplane of vibration of ultrasonic waves.
 41. A wafer processing method ofprocessing a wafer while supplying ultrasonic waves, comprising:completely dipping the wafer in a processing solution, supporting thewafer substantially perpendicular to a plane of vibration of ultrasonicwaves, and processing the wafer while swinging the wafer to cross theplane of vibration of ultrasonic waves.
 42. A wafer processing method ofprocessing a wafer while supplying ultrasonic waves, comprising:completely dipping the wafer in a processing solution, supporting thewafer substantially parallel to a plane of vibration of ultrasonicwaves, and processing the wafer while swinging the wafer to cross theplane of vibration of ultrasonic waves.
 43. A semiconductor substratefabrication method comprising: the step of forming an unporous layer ona porous layer formed on a surface of a first substrate; the step ofadhering a first substrate side of a prospective structure and a secondsubstrate prepared separately to sandwich said unporous layer betweenthe first substrate side and said second substrate; the removal step ofremoving said first substrate from the adhered structure to expose saidporous layer on a second substrate side thereof; and the etching step ofetching said porous layer while the second substrate side on which saidporous layer is exposed is completely dipped into an etching solution,and ultrasonic waves are supplied, thereby exposing a surface of thesecond substrate side, the etching step changing a strength ofultrasonic waves which act on the second substrate side.
 44. Asemiconductor substrate fabrication method comprising: the step offorming an unporous layer on a porous layer formed on a surface of afirst substrate; the step of adhering a first substrate side of aprospective structure and a second substrate prepared separately tosandwich said unporous layer between the first substrate side and saidsecond substrate; the removal step of removing said first substrate fromthe adhered structure to expose said porous layer on a second substrateside thereof; and the etching step of etching said porous layer whilethe second substrate side on which said porous layer is exposed iscompletely dipped into an etching solution, and ultrasonic waves aresupplied, thereby exposing a surface of the second substrate side, theetching step moving the second substrate side.
 45. A semiconductorsubstrate fabrication method comprising: the step of forming an unporouslayer on a porous layer formed on a surface of a first substrate; thestep of adhering a first substrate side of a prospective structure and asecond substrate prepared separately to sandwich said unporous layerbetween the first substrate side and said second substrate; the removalstep of removing said first substrate from the adhered structure toexpose said porous layer on a second substrate side thereof; and theetching step of etching said porous layer while the second substrateside on which said porous layer is exposed is completely dipped into anetching solution, and ultrasonic waves are supplied, thereby exposing asurface of the second substrate side, the etching step swinging thesecond substrate side.
 46. A semiconductor substrate fabrication methodcomprising: the step of forming an unporous layer on a porous layerformed on a surface of a first substrate; the step of adhering a firstsubstrate side of a prospective structure and a second substrateprepared separately to sandwich said unporous layer between the firstsubstrate side and said second substrate; the removal step of removingsaid first substrate from the adhered structure to expose said porouslayer on a second substrate side thereof; and the etching step ofetching said porous layer while the second substrate side on which saidporous layer is exposed is completely dipped into an etching solution,and ultrasonic waves are supplied, thereby exposing a surface of thesecond substrate side, the etching step swinging the second substrateside to cross a plane of vibration of ultrasonic waves.
 47. Asemiconductor substrate fabrication method comprising: the step offorming an unporous layer on a porous layer formed on a surface of afirst substrate; the step of adhering a first substrate side of aprospective structure and a second substrate prepared separately tosandwich said unporous layer between the first substrate side and saidsecond substrate; the removal step of removing said first substrate fromthe adhered structure to expose said porous layer on a second substrateside thereof; and the etching step of etching said porous layer whilethe second substrate side on which said porous layer is exposed iscompletely dipped into an etching solution and supported substantiallyperpendicular to a plane of vibration of ultrasonic waves, andultrasonic waves are supplied, thereby exposing a surface of the secondsubstrate side, the etching step swinging the second substrate side tocross the plane of vibration of ultrasonic waves.
 48. A semiconductorsubstrate fabrication method comprising: the step of forming an unporouslayer on a porous layer formed on a surface of a first substrate; thestep of adhering a first substrate side of a prospective structure and asecond substrate prepared separately to sandwich said unporous layerbetween the first substrate side and said second substrate; the removalstep of removing said first substrate from the adhered structure toexpose said porous layer on a second substrate side thereof; and theetching step of etching said porous layer while the second substrateside on which said porous layer is exposed is completely dipped into anetching solution and supported substantially parallel to a plane ofvibration of ultrasonic waves, and ultrasonic waves are supplied,thereby exposing a surface of the second substrate side, the etchingstep swinging the second substrate side to cross the plane of vibrationof ultrasonic waves.
 49. The apparatus according to claim 4, whereinswing support member are made of a material selected from the groupconsisting of a fluorine resin, vinyl chloride, polyethylene,polypropylene, polybutyleneterephthalate (PBT), and polyetheretherketone(PEEK).